Dark Ambient is often a frustrating and unrewarding genre. Whereas “regular” ambient music remains dominated by the theories and ethos of Brian Eno, managing to be both immersive and intangible, Dark Ambient’s focus on fear and oppressiveness mean it’s rarely either discreet enough to work as background music, nor has it the melodic elegance that made Music For Airports such a haunting work. Maybe a comparison with standard Ambient is unfair, and misses the we-wanna-scare-you point, and there are exceptions (KTL, William Fowler Collins, Lustmord), but for the most part Dark Ambient seems hamstrung by its own focus on being unsettling, and over the kind of track lengths used in ambient music, it quickly becomes dull, overbearing or irritatingly oblique.

That said, any genre can deliver remarkable results if one applies a robust and clearly thought-out concept, and that is exactly what Lull & Beta Cloud did in 2008 on their limited-release CD Circadian Rhythm Disturbance, which has been given the reissue treatment by Cold Spring. Lull — better known as Napalm Death’s Mick Harris — and Beta Cloud’s Carl Pace explore the state of insomnia, and their deep bass drones and snippets of intangible voices and sound effects recreate that dreadful state, when your mind hovers between wakefulness and near-sleep and where every sound from outside is too quiet to latch onto but loud enough to jar every sense in your body. The duo’s moody, fiercely tense sonic expanse, in which everything progresses in a state of near-stasis yet remains deeply involving, manages to eschew the clichés of “dark” music to create something that is so conceptually relevant it slips under your skin and haunts your thoughts without you even noticing.

If Harris and Pace’s take on the concept of “Circadian Rhythm Disturbance” is haunting, albeit whilst relying on the listener’s foreknowledge of the ideas contained within, Andrew Liles’s curious “remix” (the quotation marks are necessary) takes things to a different level altogether. A better word for what Liles does would be “destruction,” as he chops up the doom-like drone of the original like a madman equipped with a pair of scissors and promptly ups the angst and the noise. Disturbing, ear-shattering samples and found sounds crash into the mix, tearing any sense of equilibrium to pieces and leaving gaping holes of morose silence. The sounds Liles introduces are often unrecognizable, distorted to the point of atonality in the manner of Jason Lescalleet and Graham Lambkin’s Air Supply album. Sudden surges sound like motor vehicles accelerating, intensifying the disorientation and near-physical sickness of insomnia.

Circadian Rhythm Disturbance was a pretty brilliant approach to Dark Ambient in and of itself, meriting comparison with Thomas Köner at his most atmospheric. With Liles onboard to fuck things up in even more unsettling and intense ways, it has grown into a messy, haunting and unrelentingly powerful beast.